Inclusion of Polymers within the Crystal Structure of Tris(o-phenylenedioxy)cyclotriphosphazene

Tris(o-phenylenedioxy)cyclotriphosphazene was found to form hexagonal host−guest inclusion adducts (clathrates) with the polymers: cis-1,4-polybutadiene, trans-1,4-polyisoprene, polyethylene, poly(ethylene oxide), and polytetrahydrofuran. Single-crystal X-ray diffraction studies of both the polyethylene and poly(ethylene oxide) inclusion adducts revealed the presence of individual polymer chains extended along tunnel-like voids within the host lattice. Both polyethylene and poly(ethylene oxide) were incommensurate within the tunnel-like voids preventing the exact elucidation of the polymer conformation. Average repeat unit lengths calculated for these polymers suggest that both are in an extended conformation. Both the polyethylene and poly(ethylene oxide) adducts crystallized from benzene in the space group P63/m. Inclusion adducts of the five different polymers were examined by differential scanning calorimetry (DSC) and powder X-ray diffraction. In each case, the melting point of the inclusion adduct was higher than either the melting point of the pure polymer or the pure host. The melting points of oligomeric polyethylene and poly(ethylene oxide) inclusion adducts increased as the molecular weight of the included oligomers increased. Removal of cis-1,4-polybutadiene and poly(ethylene oxide) from the host lattice was achieved through chemical decomposition of tris(o-phenylenedioxy)cyclotriphosphazene. Linear polybutadiene was separated from a mixture with highly branched polybutadiene through selective adduct formation.